Projector

ABSTRACT

The projector appropriately generates white light from a laser light source and uses the white light for image display. A white light generator that generates white light from blue light and yellow light includes a dichroic mirror that is irradiated with blue light from a blue laser, a first condenser lens that focuses the blue light that has passed through the dichroic mirror, a diffusion plate that diffuses the focused blue light, a second condenser lens that focuses the blue light obtained by allowing the diffused blue light to pass through the dichroic mirror, and a phosphor that is irradiated with the focused blue light to emit yellow light; the diffusion plate is an alumina ceramic plate; the dichroic mirror has a first region that transmits one of the blue light and the yellow light and reflects the other and a second region that reflects or transmits both.

TECHNICAL FIELD

The present invention relates to a projector using a laser light source.

BACKGROUND ART

As a background art of a projector using a laser as a light source,there is Patent Document 1. Patent Document 1 discloses a projector thatuses white light generated by using blue light from a laser light sourceand yellow fluorescence including red light and green light for imagedisplay, requires two blue laser light sources, uses a dichroic mirrorthat reflects the blue light from a first blue laser light source andtransmits the yellow fluorescence emitted from a fluorescent plate byusing the light from a second blue laser light source as excitationlight, and combines the blue light and the yellow fluorescence togenerate white light.

CITATION LIST Patent Document

Patent Document 1: JP 2017-15966 A

SUMMARY OF THE INVENTION Problems to be Solved by the Invention

In Patent Document 1, it is necessary to arrange blue lasers at twodifferent positions, and the problem that the cost is high and the lightsource apparatus is large is not considered.

An object of the present invention is to provide a projector that moreappropriately generates white light from a laser light source.

Solutions to Problems

The present invention has been made in view of the background art andthe problems described above, and as an example, there is provided aprojector including: a white light generator that uses a blue laser as alight source to generate blue light and yellow light based on the bluelaser and generates white light including the generated blue light andyellow light; and an optical system that modulates light based on thewhite light generated by the white light generator with an image displayelement and projects the modulated light, wherein the white lightgenerator is configured to include: a dichroic mirror that is irradiatedwith the blue light from the blue laser as the light source; a firstcondenser lens that focuses blue light being reflected by or passingthrough the dichroic mirror; a diffusion plate that diffuses the bluelight focused by the first condenser lens; a second condenser lens thatfocuses the blue light passing through or being reflected by thedichroic mirror; a phosphor that is irradiated with the blue lightfocused by the second condenser lens to emit yellow light, wherein thediffusion plate is an alumina ceramic plate, wherein the dichroic mirrorhas a first region having a characteristic of transmitting one of theblue light and the yellow light and reflecting the other and a secondregion having a characteristic of reflecting or transmitting both theblue light and the yellow light, wherein the blue light included in thewhite light output by the white light generator is obtained by allowingthe blue light diffused by the diffusion plate to pass through the firstcondenser lens and performing reflection or transmission of the dichroicmirror, and wherein the yellow light included in the white light outputby the white light generator is obtained by allowing the yellow lightemitted from the phosphor to pass through the second condenser lens andperforming reflection or transmission of the dichroic mirror.

Effects of the Invention

According to the present invention, it is possible to provide aprojector that more appropriately generates white light from a laserlight source and to use the projector for image display.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a configuration diagram illustrating an optical system of aprojector according to a first embodiment.

FIG. 2A is a configuration diagram of a light source apparatus and adiagram illustrating transmission/reflection characteristics of adichroic mirror according to the first embodiment.

FIG. 2B is an example of an emission spectrum of a blue laser accordingto the first embodiment.

FIG. 2C is an example of an emission spectrum of a yellow phosphoraccording to the first embodiment.

FIG. 3 is a diagram illustrating the principle of increasing a B lightutilization rate by division of transmission and reflection regions ofthe dichroic mirror according to the first embodiment.

FIG. 4 is a diagram illustrating a method of coating a B transmitting/Yreflecting region and a totally reflecting region of the dichroic mirroraccording to the first embodiment and a transmittance characteristic ofeach region.

FIG. 5 is a configuration diagram of a light source apparatus and adiagram illustrating transmission/reflection characteristics of adichroic mirror according to a second embodiment.

FIG. 6 is a diagram illustrating a method of coating a B reflecting/Ytransmitting region and a totally transmitting region of the dichroicmirror according to the second embodiment and a transmittancecharacteristic of each region.

FIG. 7 is a configuration diagram of a light source apparatus and adiagram illustrating transmission/reflection characteristics of adichroic mirror according to a third embodiment.

FIG. 8 is a diagram illustrating an illuminance distribution of adiffusion plate according to the first to sixth embodiments.

FIG. 9 is a view illustrating a method of coating a B transmitting/Yreflecting region and a totally reflecting region of the dichroic mirroraccording to the third embodiment.

FIG. 10 is a configuration diagram of a light source apparatus and adiagram illustrating transmission/reflection characteristics of adichroic mirror according to a fourth embodiment.

FIG. 11 is a diagram illustrating a method of coating a B reflecting/Ytransmitting region and a totally transmitting region of the dichroicmirror according to the fourth embodiment.

FIG. 12 is a schematic configuration diagram of a light source portionof a light source apparatus according to a fifth embodiment.

FIG. 13 is a diagram illustrating a divisional configuration oftransmission/reflection regions of a dichroic mirror corresponding tothe first embodiment and a modification thereof in the fifth embodiment.

FIG. 14 is a diagram illustrating a divisional configuration oftransmission/reflection regions of a dichroic mirror corresponding tothe second embodiment and a modification thereof in the fifthembodiment.

FIG. 15 is a schematic configuration diagram of a light source portionof a light source apparatus according to a sixth embodiment.

FIG. 16 is a diagram illustrating a divisional configuration oftransmission/reflection regions of a dichroic mirror corresponding tothe first embodiment and a modification thereof in the sixth embodiment.

FIG. 17 is a diagram illustrating a divisional configuration oftransmission/reflection regions of a dichroic mirror corresponding tothe second embodiment and a modification thereof in the sixthembodiment.

FIG. 18 is a schematic diagram illustrating a cross-sectional view of analumina ceramic plate as a diffusion plate according to a seventhembodiment.

FIG. 19 is a diagram for explaining a light focusing angle θi ofincoming light and a diffusion angle θo of outgoing light with respectto the diffusion plate according to the seventh embodiment.

FIG. 20 is a diagram for explaining a definition of the diffusion angleθo of the outgoing light of the diffusion plate according to the seventhembodiment.

FIG. 21 is an explanatory diagram in which each region of a dichroicmirror according to the seventh embodiment is converted into a circularregion.

FIG. 22 is a diagram illustrating an optical path near the diffusionplate according to the seventh embodiment and illustrating arelationship of use efficiency of B light between the light focusingangle θi of the incoming light and the diffusion angle θo of theoutgoing light.

FIG. 23 is a type comparison table of the diffusion plate according tothe seventh embodiment.

MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments according to the present invention will bedescribed with reference to the drawings.

First Embodiment

FIG. 1 is a configuration diagram illustrating an optical system of aprojector according to the present embodiment. In FIG. 1, an opticalsystem 1 of the projector mainly includes a light source apparatus 2, anillumination optical system 3, a color separating optical system 4,image display elements 6R, 6G, and 6B, a light combining optical system7 as a combining optical system, and a projection lens 8 as a projectionoptical system.

The overall operations of the optical system of the projector will bedescribed with reference to FIG. 1. The light source apparatus 2 will bedescribed later, but from the light source apparatus 2, it is possibleto obtain light beams of white light W (in addition, the white light isalso referred to as “W light”) which is B+Y light in which blue light B(light in a blue band, hereinafter also referred to as “B light”) andfluorescence Y (hereinafter, also referred to as yellow light “Y light”)are added. Herein, the fluorescence Y is yellow fluorescence that alsoincludes light in a green band and light in a red band. The light beamsof the white light W are divided into a plurality of lights by aplurality of lens cells of a multi-lens 31 of the illumination opticalsystem 3 and are efficiently guided to a second multi-lens 32 and apolarization conversion element 33. Then, the light is polarized in apredetermined polarization direction by the polarization conversionelement 33. The polarized light is focused by a light focusing lens 34and incident on the color separating optical system 4.

In the color separating optical system 4, first, the dichroic mirror 41Bis irradiated with blue light B, the blue light B (light in a blue band)in the irradiated white light W is reflected, and green light G (lightin a green band, hereinafter also referred to as “G light”) and redlight R (light in a red band, hereinafter also referred to as “R light”)are allowed to pass. The reflected B light is reflected by a reflectionmirror 42A, is allowed to pass through a condenser lens 5B, and isincident on the image display element 6B. On the other hand, withrespect to the G light and the R light passing through a dichroic mirror41B, the G light is reflected by and the R light is allowed to passthrough a dichroic mirror 41G. The reflected G light is allowed to passthrough a condenser lens 5G and is incident on the image display element6G. In addition, the R light passing through the dichroic mirror 41G isfocused by a relay lens 43 and then reflected by a reflection mirror42B. The reflected R light is focused again by a relay lens 44 and isreflected by a reflection mirror 42C. The reflected R light is furtherfocused by a relay lens 5R and is incident on the image display element6R. Each image display element forms an image by modulating the lightintensity for each pixel in response to an image signal (notillustrated) with respect to the incoming light and generates outgoinglight by reflection or transmission. In addition, the example of FIG. 1discloses an example of a transmission type image display element. The Blight, the G light, and the R light emitted from the respective imagedisplay elements are combined into color image light by the lightcombining optical system 7 and reach a screen (not illustrated) afterpassing through the projection lens 8. That is, the optical image formedby the image display element is expanded and projected on the screen(not illustrated).

Next, referring to FIG. 2A, detailed description of the light sourceapparatus 2 in the present embodiment will be made. FIG. 2A illustratesa conceptual diagram illustrating transmission/reflectioncharacteristics of a dichroic mirror 24 at a position corresponding tothe optical axis 1 by extracting a portion of the light source apparatus2 of FIG. 1. In FIG. 2A, a light source 21 is a blue laser (BL), andblue laser light (B light) is emitted by setting the optical axis 1 as acenter. Then, the B light beam is focused and allowed to overlap by thelens 22, and the B light beam becomes a parallel light beam by the lens23. Then, the dichroic mirror 24 is irradiated with the B light beam.

Herein, the dichroic mirror 24 has a region having the characteristicsof the B transmitting/Y reflecting as illustrated and has a totallyreflecting region at the central portion of the dichroic mirror. Thatis, the dichroic mirror has a wide-area of the characteristics of the Blight transmission/Y light reflection. However, the dichroic mirror 24has a region of the totally reflecting characteristic partiallydifferent from the characteristic of the B light transmission/Y lightreflection. In the following description of the present invention, amongthe regions provided in the dichroic mirror of whichtransmission/reflection characteristics are divided into regions, aregion having a characteristic of occupying a wide-area is hereinafterreferred to as a “wide-area characteristic region”. In addition, in apartially narrow region, a region having a characteristic different fromthat of the “wide-area characteristic region” is hereinafter referred toas a “different characteristic region”. In the example of FIG. 2A, theregion having the characteristics of the B transmitting/Y reflecting isa “wide-area characteristic region”, and the totally reflecting regionis a “different characteristic region”. In addition, the B lighttransmission/reflection characteristics in the “wide-area characteristicregion” may be completely uniform. However, in order to eliminate colorunevenness depending on the incident angles of the right light and theleft light, a cut wavelength (for example, 50% wavelength) of thedichroic coat may be inclined in the left and right directions. In thiscase, in the description of each embodiment of the present invention,even if the cut wavelength is inclined, it is considered that the cutwavelength is included in the same “wide-area characteristic region”. Inaddition, in the description of each embodiment of the presentinvention, the “different characteristic region” describes an examplehaving a totally reflecting characteristic or a totally transmittingcharacteristic, but the dichroic coat is likely to be used for anyreason as long as the influence on the present invention is small. Evenin this case, the transmission/reflection characteristics may becompletely uniform within the “different characteristic region”.However, in order to eliminate the color unevenness depending on theincident angles of the right light and the left light, the cutwavelength (for example, 50% wavelength) may be set to be inclined inthe left and right directions. Even in this case, although if theinclination of the cut wavelength is set, it is considered that the cutwavelength is included in the same “different characteristic region”.

For example, as an example, when a case will be described in which theratio of the totally reflecting region which is a differentcharacteristic region in the B light region irradiated from the lightsource 21 to the dichroic mirror is set to about 20% of the irradiationrange of the incoming light beam, about 20% of the B light beamirradiated to the dichroic mirror 24 is reflected, and about 80% isallowed to pass. That is, in the B light beam irradiated from the lightsource 21 to the dichroic mirror 24, about 20% of the B light beamcentral portion is reflected.

The B light beam reflected by the dichroic mirror 24 is focused by thecondenser lens 25 and is irradiated to a diffusion plate 26. Then, the Blight beam diffused by the diffusion plate 26 by setting the opticalaxis 2 which is an optical axis of the condenser lens 25 as a center isallowed to pass through the condenser lens 25 and is irradiated to thedichroic mirror 24. At this time, the area of the B light beamirradiated to the dichroic mirror 24 is larger than the area of the Blight beam irradiated to the dichroic mirror 24 from the light source21. Then, in a case where the area expansion rate of the B light beamirradiated from the diffusion plate 26 to the dichroic mirror 24, forexample, the diffusion plate 26 having the area expansion rate of the Blight incident region by the diffusion plate, as an example, is 2, ofthe B light beam irradiated from the diffusion plate 26 to the dichroicmirror 24, for example, about 10% is reflected by the shape of thedifferent characteristic region, but about 90% light can be allowed topass.

On the other hand, in the B light beam irradiated from the light source21 to the dichroic mirror 24, the B light beam passing through thedichroic mirror 24 is focused by the condenser lens 27 and irradiated tothe phosphor wheel 28. The phosphor wheel 28 is coated with a phosphorthat emits Y light by setting the B light as the excitation light, andthe phosphor wheel is rotated by a motor 29 to prevent burning. Then, bysetting the optical axis 1 as a center, the Y light is emitted from thephosphor wheel 28, passes through the condenser lens 27, and isirradiated to the dichroic mirror 24. Then, the Y light beam isreflected by the dichroic mirror 24 and overlaps with the B light beamto be a W light beam which is a B+Y light beam.

In addition, is FIG. 2B, is illustrated an example of the emissionspectrum of the blue laser according to the present embodiment. Inaddition, in FIG. 2C, is illustrated an example of the emission spectrumof the yellow phosphor according to the present invention.

As described above, the light source apparatus 2 according to thepresent embodiment uses the blue laser as the light source 21 andcombines B (blue)+Y (yellow) light to generate white light W. That is,the light source apparatus 2 can also be referred to be a white lightgenerator. In addition, the dichroic mirror 24 has a region ofcharacteristic B transmitting/Y reflecting as a wide-area characteristicregion, and has a totally reflecting region as a differentcharacteristic region in the central portion of the dichroic mirror.Then, the B light is diffused by the diffusion plate 26 to expand thearea of the B light. Accordingly, it is possible to reduce the arearatio of the return light of the B light, which is light not included inthe white light W, to the light source 21, so that it is possible toincrease the B light utilization rate.

Next, an example of a method of coating the B transmitting/Y reflectingregion which is a wide-area characteristic region and the totallyreflecting region which is a different characteristic region of thedichroic mirror 24 in the present embodiment and an example of thetransmittance characteristic of each region will be described withreference to FIG. 4. FIG. 4(a) is a plan view, FIG. 4(b) is across-sectional view, FIG. 4(c) is a transmittance characteristic of theB transmitting/Y reflecting region, and FIG. 4(d) is a transmittancecharacteristic of the totally reflecting region. As illustrated in FIG.4(b), the dichroic mirror 24 can be manufactured by applying dichroiccoating having a B transmitting/Y reflecting characteristic on onesurface of a glass substrate, applying antireflection coating (ARcoating) on the opposite surface, and applying mirror coating for thetotally reflecting region thereon. As illustrated in FIG. 4(c), in the Btransmitting/Y reflecting region which is a wide-area characteristicregion, the transmittance around 455 nm which is a wavelength of the Blight is at least 95% or more and is preferably as close as possible to100%, and the transmittance of light from the green band to red bandaround 500 to 700 nm included in the Y light is to at least 5% or lessand is preferably as close as possible to 0%. In addition, asillustrated in FIG. 4D, the transmittance of the totally reflectingregion which is a different characteristic region is at least 5% or lessin the total wavelength region and is preferably as close as possible to0%.

That is, in each embodiment of the present invention, the B lighttransmission/Y light reflection characteristic denotes that thetransmittance for around 455 nm which is a wavelength of the B light isat least 95% or more, and the reflectance for the light around 500 to700 nm which is light from the green band to the red band is at least95% or more. Similarly, in each embodiment of the present invention, theB light reflection/Y light transmission characteristic denotes that thereflectance for around 455 nm which is a wavelength of the B light is atleast 95% or more, and the transmittance for the light around 500 to 700nm which is light from the green band to the red band is at least 95% ormore.

In addition, in each embodiment of the present invention, the “totallytransmitting characteristic” denotes that the transmittance in the totalwavelength region from at least around 455 nm which is a blue band to700 nm which is a red band is at least 95% or more. Similarly, in eachof the embodiments of the present invention, the “totally reflectingcharacteristic” denotes that the reflectance in the total wavelengthregion from at least around 455 nm which is a blue band to 700 nm whichis a red band is at least 95% or more.

In addition, in the following description, when the calculation of thelight utilization rate or the like is to be performed, in order tosimplify the calculation, in the case of the characteristic ofreflecting the light in a predetermined band, the calculation isperformed with 100% reflection, and in the case of the characteristic oftransmitting the light in a predetermined band, the calculation isperformed with 100% transmission.

In addition, in each embodiment of the present invention, in the“wide-area characteristic region”, the transmission characteristics andthe reflection characteristics of the B light and the Y light areconfigured to be opposite to each other. That is, in a case where thereis a characteristic of the B light transmission in the “wide-areacharacteristic region”, the Y light is configured to have a reflectioncharacteristic, so that the characteristic of the “wide-areacharacteristic region” is set as the B light transmission/Y lightreflection characteristic. In addition, in a case where there is acharacteristic of the B light reflection in the “wide-areacharacteristic region”, the Y light is configured to have a transmissioncharacteristic, so that the characteristic of the “wide-areacharacteristic region” is set as the B light reflection/Y lighttransmission characteristic.

In addition, in each embodiment of the present invention, in the“different characteristic region”, the transmission characteristics andthe reflection characteristics of the B light and the Y light areconfigured to be the same. That is, in a case where there is acharacteristic of the B light transmission in the “differentcharacteristic region”, the Y light is also configured to have atransmission characteristic, so that the characteristic of the“different characteristic region” is set as the totally transmittingcharacteristic. In addition, in a case where there is a characteristicof the B light transmission in the “different characteristic region”,the Y light is also configured to have a reflection characteristic, sothat the characteristic of the “different characteristic region” is setas the totally reflecting characteristic.

Next, the principle of increasing the B light utilization rate by theconfiguration according to the present embodiment will be described withreference to FIG. 3. FIG. 3(a) is a case where the configuration (theregion division of transmission/reflection characteristics and thediffusion plate) according to the present embodiment is not employed,and FIG. 3(b) is an example of an optical system of the light sourceapparatus in which there are the region division oftransmission/reflection characteristics and the diffusion plateaccording to the present embodiment.

In the configuration of FIG. 3(a), it is assumed that thetransmission/reflection characteristics of the dichroic mirror 24 areuniform over the total region, the B light reflectance is R1, and the Blight transmittance is T1. In this case, the B light utilization rate E1which is a ratio of the B outgoing light (B transmission light in thedrawing) to the incoming light of the B light is R1×(1−R1)=(R1×T1). Forexample, if it is assumed that R1=0.2 and T1=0.8 which are settingswhere 20% of the B light incident on the dichroic mirror 24 is reflectedand 80% is allowed to pass, the B light utilization rate E1[%]=0.2×(1−0.2)×100=16 [%].

On the other hand, in the case of the configuration of FIG. 3(b)according to the present embodiment, as illustrated in FIG. 3(c), thearea of the incident region I of the B incoming light is represented bySI, the area of the incident region O of the B diffusion light isrepresented by SO, the area of the totally reflecting region WI (thereflection characteristic R of the B light becomes R1) which is adifferent characteristic region in the incident region I of the Bincoming light is represented by SWI, and the area of the totallyreflecting region WO (the reflection characteristic R of the B lightR≈1) which is a different characteristic region in the incident region Oof the B incoming light is represented by SWO. At this time, the Bincoming light substantial reflectance R2 at the dichroic mirror 24,which is a ratio of reflection light to the B incoming light from thelaser light source, can be calculated from SWI/SI. In addition, the Bdiffusion light substantial transmittance T2 which is a ratio oftransmission to the B diffusion light can be calculated from (SO−SWO)/SOby the dichroic mirror 24. The B light utilization rate E2 isR2×T2=(SWI/SI)×((SO−SWO)/SO). Herein, SWI/SI can also be represented asthe use efficiency of the B light incident on the dichroic mirror fromthe laser light source. In addition, (SO−SWO)/SO can be represented asthe use efficiency of the B light incident on the dichroic mirror fromthe B diffusion light.

Herein, in order to compare the efficiencies of the configuration ofFIG. 3(a) and the configuration of FIG. 3(b), considered is the casewhere the settings of the B light reflectance R1 in FIG. 3(a) and the Bincoming light substantial reflectance R2 in FIG. 3(b) are allowed to beequal to each other. At this time, the condition for E2>E1 isR2×T2>R1×(1−R1). Herein, when R2 is substituted for R1, R2×T2>R2×(1−R2).When both sides are divided by R2, T2>1−R2. This can be converted into(SO−SWO)/SO>(SI−SWI)/SI. By multiplying both sides by SO,SO−SWO>(SI−SWI)×SO/SI. If SO/SI is set to α as the area expansion rateof the incident region of the diffusion light, SO−SWO>SO−SWI×α, andthus, this can be modified to SWI×α>SWO. This can be modified toSWO/SWI<α, and if SWO/SWI=β, α<β. This expression denotes that, bysetting the shape of the different characteristic region in the dichroicmirror 24 so that the ratio β of SWO which is a size of the differentcharacteristic region in the incident region O of the B diffusion lightto SWI which is a size of the different characteristic region in theincident region I of the B incoming light is not to be larger than thearea expansion rate α of the incident region of the diffusion light, theefficiency of the configuration of FIG. 3(b) can be allowed to be largerthan the efficiency of the configuration of FIG. 3(a). When the B lightutilization rate E2 is represented by an equation using α and β,E2=R2×T2=R2×(1−(R2×β/α)). That is, in the configuration of FIG. 3(b)according to the present embodiment, if only the B light utilizationrate up to the emission of the dichroic mirror 24 is considered, thelarger the area expansion rate α of the incident region of the diffusionlight is, the higher the efficiency is. The smaller the ratio β of theSWO which is a size of the different characteristic region in theincident region O of the B diffusion light to the SWI which is a size ofthe different characteristic region in the incident region I, the higherthe efficiency is.

Specifically, for example, in a case where R2=SWI/SI=0.2, the areaexpansion rate of the incident region of the diffusion light α=SO/SI=2,and the shape of the different characteristic region is β=SWO/SWI=1.2,the B light utilization rate E2 [%]=0.2×(1−(0.2×1.2/2))×100=17.2 [%],which is larger.

This is larger than the B light utilization rate E1 [%]=16 [%] of theconfiguration of FIG. 3(a) in a case where R1=0.2.

As described above, according to the present embodiment, in the lightsource apparatus that generates white light by using a blue laser as thelight source 21 and combining B+Y light, in such a configuration wherethe dichroic mirror 24 has a characteristic region of B transmitting/Yreflecting which is a wide-area characteristic region and a totallyreflecting region which is a different characteristic region provided atthe central portion, so that the transmission/reflection characteristicsare divided into regions, it is possible to increase the B lightutilization rate by diffusing the B light by the diffusion plate 26 andexpanding the area of the B light.

As described above, according to the present embodiment, it is possibleto more appropriately realize a projector that generates white lightfrom a laser light source and that is used for image display.

Second Embodiment

The present embodiment is an example in which the specifications of thecoating of the dichroic mirror of the light source apparatus in theprojector of the first embodiment are changed, and accordingly, thearrangement of the phosphor wheel and the diffusion plate is changed.

In addition, for simplifying the description, in the description of thepresent embodiment, only the points changed from the first embodimentwill be described, and the configurations and operations that are notparticularly described are the same as those of the first embodiment. Inparticular, since the configurations and operations of the opticalsystem and the image display element of the projector after generationof the white light, W light, which is B+Y light in the light sourceapparatus are the same as those in FIG. 1 of the first embodiment, andthus, the description thereof will be omitted.

FIG. 5 is a configuration diagram of the light source apparatus of theprojector and a diagram illustrating the transmission/reflectioncharacteristics of the dichroic mirror in the present embodiment. InFIG. 5, components having the same functions as those in FIG. 2 aredenoted by the same reference numerals, and thus, the descriptionthereof will be omitted. FIG. 5 is different from FIG. 2 in that thetransmission/reflection characteristics of the dichroic mirror aredifferent and that the positions of the phosphor wheel and the diffusionplate are interchanged.

In FIG. 5, the dichroic mirror 91 is irradiated with the B light beamthat has been made substantially parallel by the lens 23. Herein, asillustrated, the dichroic mirror 91 has a characteristic region of the Breflecting/Y transmitting which is a wide-area characteristic region andhas a totally transmitting region which is a different characteristicregion in the central portion of the dichroic mirror. That is, thedichroic mirror 91 has a wide region of characteristics of the B lightreflection/Y light transmission which is a wide-area characteristicregion, but has a region (different characteristic region) of totallytransmitting characteristic partially different from the characteristicof the B light reflection/Y light transmission. For example, as anexample, when a case will be described in which the ratio of the totallytransmitting region to the B light region irradiated from the lightsource 21 to the dichroic mirror is set to 20% of the total region,about 80% of the B light beam irradiated to the dichroic mirror 91 isreflected, and about 20% is allowed to pass. That is, about 20% of the Blight beam central portion of the B light beam irradiated from the lightsource 21 to the dichroic mirror 91 is transmitted. As described above,the transmission/reflection characteristics of the dichroic mirror ofthe second embodiment are different from those of the first embodiment,but the concept is common in that the same dichroic mirror has the widecharacteristic region having a predetermined transmission/reflectioncharacteristic region and the different characteristic region partiallydifferent from the predetermined transmission/reflection characteristic.

The B light beam reflected by the dichroic mirror 91 is focused by thecondenser lens 27 and is irradiated to the phosphor wheel 28. By settingthe optical axis 2 which is an optical axis of the condenser lens 27 asa center, the Y light is emitted from the phosphor wheel 28, allowed topass through the condenser lens 27, and is irradiated to the dichroicmirror 91, and the Y light beam is allowed to pass through the dichroicmirror 91.

On the other hand, in the B light beams irradiated from the light source21 to the dichroic mirror 91, the B light beam passing through thedichroic mirror 91 is focused by the condenser lens 25 and is irradiatedto the diffusion plate 26. By setting the optical axis 1 as a center,the B light beam diffused by the diffusion plate 26 is allowed to passthrough the condenser lens 25 and is irradiated to the dichroic mirror91. At this time, the area of the B light beam irradiated to thedichroic mirror 91 is larger than the area of the B light beamirradiated to the dichroic mirror 91 from the light source 21. In a casewhere the area expansion rate of the B light incident region by thediffusion plate in the B light beam irradiated from the diffusion plate26 to the dichroic mirror 91 is, for example, 2, as an example, about10% is allowed to pass due to the shape of the different characteristicregion, but about 90% can be reflected. Then, the B light beam reflectedby the dichroic mirror 91 overlaps with the Y light beam to be a B+Ylight beam. Therefore, even with the configuration of the secondembodiment, the B light utilization rate can be increased to the sameextent as the first embodiment.

FIG. 6 is a diagram illustrating a method of coating the B reflecting/Ytransmitting region and the totally transmitting region of the dichroicmirror 91 in the present embodiment and a transmittance characteristicof each region. FIG. 6(a) is a plan view, FIG. 6(b) is a cross-sectionalview, FIG. 6(c) is a transmittance characteristic of the B reflecting/Ytransmitting region, and FIG. 6(d) is a transmittance characteristic ofthe totally transmitting region. As illustrated in FIG. 6(b), thedichroic mirror 91 can be manufactured by applying AR coating on onesurface of a glass substrate and applying dichroic coating having Breflecting and Y transmitting characteristics, and AR coating for thetotally transmitting region on the opposite surface. As illustrated inFIG. 6(c), in the B reflecting/Y transmitting region, which is awide-area characteristic region, the transmittance around 455 nm whichis a wavelength of the B light is at least 5% or less and is preferablyas close as possible to 0%, and the transmittance of light from thegreen band to the red band around 500 to 700 nm included in the Y lightis at least 95% or more and is preferably as close as possible to 100%.In addition, as illustrated in FIG. 6(d), the transmittance of thetotally transmitting region, which is a region of differentcharacteristics, is at least 95% or more in the total wavelength rangeand is preferably as close as possible to 100%.

In addition, details of the principle and conditions of increasing the Blight utilization rate in the configuration of the present embodimentmay be obtained from the description of FIG. 3 of the first embodimentby replacing the “transmission” of the B light with “reflection” andreplacing the “totally reflecting” with “totally transmitting”.Specifically, the area of the incident region I of the B incoming lightin FIG. 3(c) is represented by SI, the area of the incident region O ofthe B diffusion light is represented by SO, the area of the totallytransmitting region WI (the transmission characteristic T of the B lightis T≈1) which is a different characteristic region in the incidentregion I of the B incoming light is represented by SWI, and the area ofthe totally transmitting region WO (the reflection characteristic T ofthe B light is T≈1) which is a different characteristic region in theincident region O of the B diffusion light is represented by SWO. Atthis time, the B incoming light substantial transmittance T3 which is aratio of the transmission light to the B incoming light from the laserlight source can be calculated from SWI/SI by the dichroic mirror 91. Inaddition, the B diffusion light substantial reflectance R3 which is aratio of transmission to the B diffusion light can be calculated from(SO−SWO)/SO by the dichroic mirror 91. The B light utilization rate E3in the light source apparatus according to the second embodiment isT3×R3=(SWI/SI)×((SO−SWO)/SO). In other words, even if the reflectioncharacteristic and the transmission characteristic of the B light areopposite to those of the first embodiment, the B light utilization rateE3 of the light source apparatus is not changed from the product of theuse efficiency (SWI/SI) of the B light incident on the dichroic mirrorfrom the laser light source and the use efficiency ((SO−SWO)/SO) of theB light incident on the dichroic mirror from the B diffusion light.

Then, similarly to the equation modified example of the embodiment 1E2,by changing the SO/SI by using the area expansion rate α of the incidentregion of the diffusion light and the ratio β of SWO which is a size ofthe different characteristic region in the incident region O of the Bdiffusion light to SWI which is a size of the different characteristicregion in the incident region I of the B incoming light, the B lightutilization rate E3 of the light source apparatus of the presentembodiment can also be expressed as E3=T3×R3=T3×(1−(T3×β/α)).

That is, in the configuration according to the present embodiment aswell, if only the B light utilization rate up to the emission of thedichroic mirror 91 is considered, the larger the area expansion rate αof the incident region of the diffusion light is, the higher theefficiency is. The smaller the ratio β of the SWO which is a size of thedifferent characteristic region in the incident region O of the Bdiffusion light to the SWI which is a size of the differentcharacteristic region in the incident region I, the higher theefficiency is.

As described above, according to the present embodiment, in the lightsource apparatus that generates white light by using a blue laser as thelight source 21 and combining B+Y light, in such a configuration wherethe dichroic mirror 24 has a characteristic region of B reflecting/Ytransmitting which is a wide-area characteristic region and a totallytransmitting region which is a different characteristic region providedat the central portion, so that the transmission/reflectioncharacteristics are divided into regions, it is possible to increase theB light utilization rate by diffusing the B light by the diffusion plate26 and expanding the area of the B light

As described above, according to the present embodiment, even with aconfiguration different from that of the first embodiment, it ispossible to realize a projector that more appropriately generates whitelight from a laser light source and that is used for image display tothe same degree as the first embodiment.

Third Embodiment

The present embodiment describes an example in which, in the projectoraccording to the first embodiment, the different characteristic regionin the dichroic mirror in the light source apparatus is arranged at aposition offset from a central portion where the optical axis 2 which isan optical axis of the condenser lens 25 and the dichroic mirror are incontact with each other.

FIG. 7 is a configuration diagram of the light source apparatus and adiagram illustrating transmission/reflection characteristics of thedichroic mirror according to the present embodiment. In FIG. 7,components having the same functions as those in FIG. 2 are denoted bythe same reference numerals, and thus, the description thereof will beomitted.

In FIG. 2 of the first embodiment, the position of the differentcharacteristic region in the dichroic mirror is arranged near thecentral portion where the optical axis 2 and the dichroic mirror are incontact with each other, and in contrast, in FIG. 7 of the presentinvention, the position of the different characteristic region islocated at the position offset from the central portion where theoptical axis 2 and the dichroic mirror are in contact with each other.

In order to change the position of the different characteristic regionoffset from the central portion where the optical axis 2 and thedichroic mirror are in contact with each other in this manner, simply,within the range where the B light incoming light from the B color laserlight source 21 is incident, the different characteristic region may bearranged at a position offset from the central portion where the opticalaxis 2 and the dichroic mirror are in contact with each other. Inaddition, by arranging the optical axis 1 of the B color laser lightsource 21 to be offset from the optical axis 3 having a mirrorarrangement with respect to the optical axis 2 of the condenser lens 25and the dichroic mirror, t the different characteristic region can bearranged to be further offset from the optical axis 2. In FIG. 7,illustrated is an example in which both the offset of the optical axis 1of the laser light source 21 and the offset from the central portion ofthe different characteristic region are employed.

In FIG. 7, the B light beam allowed to be parallel by the lens 23 isirradiated to the dichroic mirror 92. Herein, as illustrated, thedichroic mirror 92 has a B transmitting/Y reflecting characteristicregion, which is a wide-area characteristic region, and is prepared fora position offset from the position where the totally reflecting region,which is a different characteristic region, is in contact with theoptical axis 2. For example, when the ratio of the totally reflectingregion to the B light region irradiated from the light source 21 to thedichroic mirror is set to 20% of the total, about 20% of the B lightbeam irradiated to the dichroic mirror 92 is reflected, and about 80% isallowed to pass. That is, in the B light beam irradiated from the lightsource 21 to the dichroic mirror 92, 20% of the portion offset from thecenter of the B light beam is reflected.

The B light beam reflected by the dichroic mirror 92 is diffused by thediffusion plate 26 and is irradiated to the dichroic mirror 92. At thistime, the area of the B light beam irradiated to the dichroic mirror 92is larger than the area of the B light beam irradiated to the dichroicmirror 92 from the light source 21.

Next, in the B light beam irradiated from the diffusion plate 26 to thedichroic mirror 92, the ratio of the B light beam reflected from thedifferent characteristic region and the ratio of the B light beampassing through the wide region characteristic region are calculatedbased on only the area ratio. For example, such a configuration isconsidered that, in a case where the area expansion rate of the B lightincident region by the diffusion plate is 2 by the calculation of thearea ratio, as an example, about 10% is reflected and about 90% isallowed to pass due to the shape of the different characteristic region.Herein, unlike the first embodiment, in the third embodiment, theposition of the different characteristic region is offset from thecentral portion where the optical axis 2 and the dichroic mirror are incontact with each other. Herein, in FIG. 8, illustrated is anilluminance distribution diagram of light emitted from the diffusionplate 26. As illustrated in FIG. 8, the illuminance is decreased as theposition is deviated from the center position. Then, the position of thedifferent characteristic region is arranged to be offset from thecentral portion where the optical axis 2 and the dichroic mirror are incontact with each other as in the third embodiment, and thus, even ifthe area of the different characteristic region is the same as that ofthe first embodiment, in the B diffusion light from the diffusion plate26, the B diffusion light of the portion thereof being reflected by thedichroic mirror 92 and returning to the light source 21 has a relativelysmall intensity at the peripheral angle instead of the peak intensity atthe central angle in FIG. 8, so that it is possible to reduce the lightreturning to the laser light source as compared with FIG. 2 of the firstembodiment. For example, in such a configuration where, if the relativeratio effect of the diffusion light intensity in FIG. 8 due to thisoffset is set to 50%, the area expansion rate of the B light incidentregion by the diffusion plate is 2, and only in the calculation of thearea ratio, about 10% is reflected and about 90% is allowed to pass dueto the shape of the different characteristic region, so that about 5% ofthe B light beam irradiated from the diffusion plate 26 to the dichroicmirror 92 is reflected and about 95% is allowed to pass in considerationof the actual intensity distribution of FIG. 8.

On the other hand, in the B light beam irradiated from the light source21 to the dichroic mirror 92, the B light beam transmitted through thedichroic mirror 92 is irradiated to the phosphor wheel 28. Then, bysetting the optical axis 3 which is an optical axis of the condenserlens 27 as a center, the Y light is emitted from the phosphor wheel 28and is irradiated to the dichroic mirror 92. Then, the Y light beam isreflected by the wide-area characteristic region of the dichroic mirror92 and overlaps with the B light beam to be a B+Y light beam.

FIG. 9 is a diagram illustrating a method of coating the Btransmitting/Y reflecting region which is a wide-area characteristicregion and the totally reflecting region which is a differentcharacteristic region of the dichroic mirror 92 in the presentembodiment. FIG. 9(a) is a plan view, and FIG. 9(b) is a cross-sectionalview. As illustrated in FIG. 9(b), the dichroic mirror 92 can bemanufactured by applying dichroic coating having B reflecting/Ytransmitting characteristics on one surface of a glass substrate,applying AR coating on the opposite surface, and applying mirror coatingfor the totally transmitting region thereon.

According to the present embodiment described above, in the light sourceapparatus that generates white light by combining B+Y light by using ablue laser as the light source 21, in such a configuration where thedichroic mirror has a characteristic region of the B transmitting/Yreflecting which is a wide-area characteristic region and the totallyreflecting region which is a different characteristic region is arrangedto be offset from a position to be in contact with the optical axis 2which is an optical axis of the condenser lens 25, so that thetransmission/reflection characteristics are divided into regions, it ispossible to increase the B light utilization rate by diffusing the Blight by the diffusion plate 26 and expanding the area of the B light.

As described above, according to the present embodiment, it is possibleto increase the B light utilization rate as compared with the firstembodiment, and it is possible to realize a projector that moreappropriately generates white light from a laser light source and thatis used for image display.

Fourth Embodiment

The present embodiment describes an example in which, in the projectoraccording to the second embodiment, the different characteristic regionin the dichroic mirror in the light source apparatus is arranged at aposition offset from a central portion where the optical axis 3 which isan optical axis of the condenser lens 25 and the dichroic mirror are incontact with each other.

FIG. 10 is a configuration diagram of the light source apparatus and adiagram illustrating transmission/reflection characteristics of thedichroic mirror according to the present embodiment. In FIG. 10,components having the same functions as those in FIG. 5 are denoted bythe same reference numerals, and thus, the description thereof will beomitted.

In FIG. 5 of the second embodiment, the position of the differentcharacteristic region in the dichroic mirror is arranged near thecentral portion where the optical axis 3 and the dichroic mirror are incontact with each other, and in contrast, in FIG. 10 of the presentinvention, the position of the different characteristic region islocated at the position offset from the central portion where theoptical axis 3 and the dichroic mirror are in contact with each other.

In order to change the position of the different characteristic regionoffset from the central portion where the optical axis 2 and thedichroic mirror are in contact with each other in this manner, simply,within the range where the B light incoming light from the B color laserlight source 21 is incident, the different characteristic region may bearranged at a position offset from the central portion where the opticalaxis 3 and the dichroic mirror are in contact with each other. Inaddition, by arranging the optical axis 1 of the B color laser lightsource 21 to be offset from the optical axis 3, the differentcharacteristic region can be arranged to be further offset from theoptical axis 3. In FIG. 10, illustrated is an example in which both theoffset of the optical axis 1 of the laser light source 21 and the offsetfrom the central portion of the different characteristic region areemployed.

In FIG. 10, the B light beam allowed to be parallel by the lens 23 isirradiated to the dichroic mirror 93. Herein, as illustrated, thedichroic mirror 93 has a B reflecting/Y transmitting characteristicregion, which is a wide-area characteristic region, and is prepared fora position offset from the position where the totally transmittingregion, which is a different characteristic region, is in contact withthe optical axis 3. For example, when the ratio of the totallytransmitting region, which is a different characteristic region, to theB light region irradiated from the light source 21 to the dichroicmirror is set to 20%, about 80% of the B light beam irradiated to thedichroic mirror 93 is reflected, and about 20% is allowed to pass. Thatis, in the B light beam irradiated from the light source 21 to thedichroic mirror 93, about 20% of the portion offset from the center ofthe B light beam is allowed to pass.

The B light beam reflected by the dichroic mirror 93 is irradiated tothe phosphor wheel 28. By setting the optical axis 2 which is an opticalaxis of the condenser lens 27 as a center, Y light is emitted from thephosphor wheel 28 and irradiated to the dichroic mirror 93, and the Ylight beam is allowed to pass through the dichroic mirror 93.

On the other hand, in the B light beam emitted from the light source 21to the dichroic mirror 93, the B light beam passing through the dichroicmirror 93 is irradiated to the diffusion plate 26, and by setting theoptical axis 3 which is an optical axis of the condenser lens 25 as acenter, the B light beam diffused by the diffusion plate 26 isirradiated to the dichroic mirror 93. At this time, the area of the Blight beam irradiated to the dichroic mirror 93 is larger than the areaof the B light beam irradiated to the dichroic mirror 93 from the lightsource 21.

Next, in the B light beam irradiated from the diffusion plate 26 to thedichroic mirror 93, the ratio of the B light beam passing through thedifferent characteristic region and the ratio of the B light beamreflected from the wide-area characteristic region are calculated basedon only the area ratio. For example, such a configuration is consideredthat, in a case where the area expansion rate of the B light incidentregion by the diffusion plate is 2, as an example, 10% is allowed topass and about 90% is reflected due to the shape of the differentcharacteristic region. Herein, unlike the second embodiment, in thepresent embodiment, the position of the different characteristic regionis offset from the central portion where the optical axis 3 and thedichroic mirror are in contact with each other. Herein, as illustratedin FIG. 8, the illuminance of the light emitted from the diffusion plate26 is decreased as the position is deviated from the center position.Then, the position of the different characteristic region is arranged tobe offset from the central portion where the optical axis 3 and thedichroic mirror are in contact with each other as in the thirdembodiment, and thus, even if the area of the different characteristicregion is the same as that of the second embodiment, in the B diffusionlight from the diffusion plate 26, the B diffusion light of the portionthereof being allowed to pass through the dichroic mirror 93 andreturning to the light source 21 has a relatively small intensity at theperipheral angle instead of the peak intensity at the central angle inFIG. 8, so that it is possible to reduce the light returning to thelaser light source as compared with FIG. 5 of the second embodiment. Forexample, in such a configuration where, if the relative ratio effect ofthe diffusion light intensity in FIG. 8 due to this offset is set to50%, the area expansion rate of the B light incident region by thediffusion plate is 2, and only in the calculation of the area ratio,about 10% is allowed to pass and about 90% is reflected due to the shapeof the different characteristic region, so that about 5% of the B lightbeam irradiated from the diffusion plate 26 to the dichroic mirror 93 isallowed to pass and about 95% is reflected in consideration of theactual intensity distribution of FIG. 8.

Then, the B light beam reflected by the wide-area characteristic regionof the dichroic mirror 93 is allowed to overlap with the Y light beam tobecome a B+Y light beam.

FIG. 11 is a diagram illustrating a method of coating the B reflecting/Ytransmitting region, which is a wide-area characteristic region, and thetotally transmitting region, which is a different characteristic region,of the dichroic mirror 93 in the present embodiment. FIG. 11(a) is aplan view, and FIG. 11(b) is a cross-sectional view. As illustrated inFIG. 11(b), the dichroic mirror 93 can be manufactured by applying ARcoating on one surface of a glass substrate and applying dichroiccoating having B reflecting/Y transmitting characteristics and ARcoating for the totally transmitting region on the opposite surface.

According to the present embodiment described above, in the light sourceapparatus that generates white light by combining B+Y light by using ablue laser as the light source 21, in such a configuration where thedichroic mirror 93 has a characteristic region of the B transmitting/Yreflecting which is a wide-area characteristic region and the totallyreflecting region which is a different characteristic region is arrangedto be offset from a position to be in contact with the optical axis 3which is an optical axis of the condenser lens 25, so that thetransmission/reflection characteristic is region-divided, it is possibleto increase the B light utilization rate by diffusing the B light by thediffusion plate 26 and expanding the area of the B light.

As described above, according to the present embodiment, it is possibleto increase the B light utilization rate as compared with the secondembodiment, and it is possible to realize a projector that moreappropriately generates white light from a laser light source and thatis used for image display.

Fifth Embodiment

The present embodiment describes an example in which, in the projectordescribed in the first to fourth embodiments, dimming and/or colortoning are performed by changing intensities of lasers by using adivisional configuration of a transmission/reflection region of adichroic mirror and a plurality of the lasers as light sources.

FIG. 12 is a schematic configuration diagram of a light source portionof the light source apparatus according to the present embodiment. FIG.12 illustrates details of the configuration of the light source 21 inthe configuration of the light source apparatus of FIG. 2A, FIG. 5, FIG.7, or FIG. 10. More specifically, two light sources 21-1 and 21-2 areused as the light sources 21, the respective light sources are driven bythe power supply 1 (20-1) and the power supply 2 (20-2), and acontroller 10 controlling the power supply 1 and the power supply 2 isprovided.

FIG. 13 is a diagram illustrating a divisional configuration of thetransmission/reflection region of the dichroic mirror corresponding tothe first embodiment (the configuration of FIG. 2A) and a modificationthereof. FIG. 13(a) is a configuration corresponding to the firstembodiment. In FIG. 13(a), an irradiation region E21-1 irradiated withthe B light from the light source 21-1 and an irradiation region E21-2irradiated with the B light from the light source 21-2 are provided inthe respective regions that extend over the B transmitting/Y reflectingregion (wide-area characteristic region M) and the totally reflectingregion (different characteristic region W). In addition, the combinedregion of the irradiation region E21-1 irradiated with the B light fromthe light source 21-1 and the irradiation region E21-2 irradiated withthe B light from the light source 21-2 corresponds to the region I ofFIG. 3(c). In addition, the B diffusion light incident regionillustrated in FIG. 13(a) corresponds to the region O in FIG. 3(c).

In the example of FIG. 13(a), the regions are arranged symmetrically tothe left and right, and thus, the ratio between the wide-areacharacteristic region M and the different characteristic region W in theirradiation region E21-1 and the ratio between the wide-areacharacteristic region M and the different characteristic region W in theirradiation region E21-2 are the same as each other. Therefore, when thelaser intensities of the light sources 21-1 and 21-2 are changed, it ispossible to realize a dimming function of adjusting the intensity of thelight output from the light source apparatus 2 without changing theratio between the B light and the Y light output from the light sourceapparatus 2.

FIG. 13(b) is a modified example of the region division of FIG. 13(a),and unlike FIG. 13(a), the totally reflecting region which is adifferent characteristic region W is wide in the width direction of thepaper and corresponds to the region (corresponding to the region I inFIG. 3(c)) in which the irradiation region E21-1 irradiated with the Blight from the light source 21-1 and the irradiation region E21-2irradiated with the B light from the light source 21-2 are combined. Inthe example of FIG. 13(b), since the different characteristic region Wis included in the region I, the different characteristic region Wcorresponds to both the region WI and the region WO in the example ofFIG. 3(c). As described in the first embodiment, in the light sourceapparatus 2, as the ratio β of SWO which is the size of the differentcharacteristic region in the incident region O of the B diffusion lightto SWI which is the size of the different characteristic region in theincident region I of the B incoming light becomes smaller, the B lightutilization rate as a light source apparatus becomes better. Herein, byallowing the different characteristic region W to be included in theregion I, β=1 can be set, and thus, it is possible to minimize β.

In addition, the B light use efficiency E2 of the configuration of FIG.3(b) described in the first embodiment is always higher than the B lightuse efficiency E1 of the configuration of FIG. 3(a) when β/α is smallerthan 1. Then, if β=1 can be achieved by allowing the differentcharacteristic region W to be included in the region I, α is larger than1 due to the effects of the condenser lens 25 and the diffusion plate26, and thus, the B light use efficiency of the configuration of FIG.3(b) t is always higher than that of the configuration of FIG. 3(a).

Then, if the configuration is such that the different characteristicregion W is included in the region I as illustrated in FIG. 13(b), it ispossible to allow the B light utilization rate to be higher than that ofthe configuration in which the different characteristic region W is notincluded in the region I as illustrated in FIG. 13(a).

In addition, in the configuration of FIG. 13(a), since the differentcharacteristic region W is elongated at the vertical boundary betweenthe irradiation region E21-1 and the irradiation region E21-2, in a casewhere the position of the irradiation region E2-1, the position of theirradiation region E21-2, and the relative position of the dichroicmirror in the left and right directions are greatly deviated due to theassembly accuracy of the optical components and the like, the ratiobetween the wide-area characteristic region M and the differentcharacteristic region W in the irradiation region E21-1 and the ratiobetween the wide-area characteristic region M and the differentcharacteristic region W in the irradiation region E21-2 is greatlychanged. For example, in a case where the B light irradiated to thetotally reflecting region which is a different characteristic region Wis only one of the left and right light sources due to the deviation ofthe relative position, when the power supply that controls the one laserlight source fails, only the light that has passed through the wide-areacharacteristic region M in the light incident on the dichroic mirrorfrom the light source is used, and thus, one (the example in FIG. 13(a))of the B light or the Y light from the light source apparatus 2 isoutput, in this case, only the Y light is output, so that it isimpossible to generate white light. In contrast, in the configurationillustrated in FIG. 13(b), since the totally reflecting region, which isa different characteristic region W is wide in the width direction, evenif the deviation of the relative position in the left-right directionoccurs, the B light irradiated to the totally reflecting region which isa different characteristic region W is unlikely to be only one of theleft and right light sources.

Accordingly, in the configuration of FIG. 13(b), even in a case wherethe power supply for controlling one laser light source is out of order,it is possible to avoid the phenomenon that the output light from thelight source apparatus 2 becomes one of the B light and the Y light.

In addition, FIG. 13(c) is a modified example of still another regiondivision. In the example of FIG. 13(c), unlike the examples of FIGS.13(a) and 13(b), the totally reflecting region which is a differentcharacteristic region W is configured to be asymmetrical on the left andright. Accordingly, the ratio between the wide-area characteristicregion M and the different characteristic region W in the irradiationregion E21-1 and the ratio between the wide-area characteristic region Mand the different characteristic region W in the irradiation regionE21-2 are allowed to be different from each other. Accordingly, theratio between the B light and the Y light in which the B light from thelight source 21-1 finally contributes to the output light of the lightsource apparatus 2 and the ratio between the B light and the Y light inwhich the B light from the light source 21-2 finally contributes to theoutput light of the light source apparatus 2 can be allowed to bedifferent. Then, the light intensity of the light source 21-1 isvariably controlled by controlling the power supply 1, or the lightintensity of the light source 21-2 is variably controlled by controllingthe power supply 2, and thus, by changing the relative ratio between thelight intensity of the light source 21-1 and the light intensity of thelight source 21-2, it is possible to control both the color and theintensity of the light output from the light source apparatus 2. Thatis, a color toning function and a dimming function of the light outputfrom the light source apparatus 2 can be realized.

In the example of FIG. 13(c), since the different characteristic regionW is included in the region (region I) in which the irradiation regionE21-1 and the irradiation region E21-2 are combined, there is also anadvantage in that the B light utilization rate is high.

In addition, FIG. 13(d) is a modified example of still another regiondivision. In the example of FIG. 13(d), similarly to the example of FIG.13(c), the ratio between the wide-area characteristic region M and thedifferent characteristic region W in the irradiation region E21-1 andthe ratio between the wide-area characteristic region M and thedifferent characteristic region W in the irradiation region E21-2 areallowed to be different from each other. Therefore, similarly to theexample of FIG. 13(c), the light intensity of the light source 21-1 isvariably controlled by controlling the power supply 1, or the lightintensity of the light source 21-2 is variably controlled by controllingthe power supply 2, and thus, by changing the relative ratio between thelight intensity of the light source 21-1 and the light intensity of thelight source 21-2, it is possible to control both the color and theintensity of the light output from the light source apparatus 2.

In addition, in the example of FIG. 13(d), as the differentcharacteristic region W (totally reflecting region), an independentshape is provided for each irradiation region from the left and rightlight sources. In addition, the respective different characteristicregions W are provided at the positions apart from the boundaries of theirradiation regions from the left and right light sources. Accordingly,it is possible to provide a configuration in which, due to theassembling accuracy of the optical components, even if the relativepositions of the different characteristic region W of the dichroicmirror to the position of the irradiation region E21-1 and the positionof the irradiation region E21-2 are deviated in the horizontal directionor deviated in the vertical direction, the ratio between the wide-areacharacteristic region M and the different characteristic region W in theirradiation region E21-1 and the ratio between the wide-areacharacteristic region M and the different characteristic region W in theirradiation region E21-2 are hard to change.

That is, the example of FIG. 13(d) is a preferable mode because it ispossible to achieve both the realization of the color toning functionand the dimming function of the light output from the light sourceapparatus 2 and the reduction of the influence of the deviation betweenthe position of the irradiation region E21-1 and the position of theirradiation region E21-2 and the relative position of the differentcharacteristic region W of the dichroic mirror due to the assemblyaccuracy of the optical components, and the like.

In addition, in the example of FIG. 13(d), since the differentcharacteristic region W is included in the region (region I) in whichthe irradiation region E21-1 and the irradiation region E21-2 arecombined, there is also an advantage in that the B light utilizationrate is high.

As described above, a plurality of the examples that are the examples ofthe shape of the different characteristic region W of the firstembodiment (the configuration of FIG. 2A) and the modified examplesthereof have been described with reference to FIG. 13. In addition, themodified examples thereof can also be applied to the case where theoptical axis 1 of the light source 21 is offset with respect to theoptical axis 3 having a mirror relationship with the optical axis 2 ofthe condenser lens 25 as illustrated in FIG. 7 of the third embodiment.

In addition, FIG. 14 is a diagram illustrating a divisionalconfiguration of the transmission/reflection region of a dichroic mirrorcorresponding to the second embodiment and the modified examplesthereof. FIG. 14(a) is a configuration corresponding to the secondembodiment. FIG. 14(a) illustrates the example of a case where theconfiguration illustrated in FIG. 12 is employed as the light source 21in the configuration of FIG. 5 of the second embodiment, and FIGS.14(b), 14(c), and 14(d) are the modified examples thereof.

Herein, the examples of the divisional configuration of thetransmission/reflection region of the dichroic mirror illustrated inFIGS. 14(a), 14(b), 14(c), and 14(d) are obtained from the examples ofthe divisional configuration of the transmission/reflection region ofthe dichroic mirror illustrated in FIGS. 13(a), 13(b), 13(c), and 13(d)by replacing the characteristics of the wide-area characteristic regionM with B reflecting/Y transmitting and replacing the characteristics ofthe different characteristic region W with totally transmitting so as tocorrespond to the second embodiment. If the description of each FIG. 13is replaced in response to the change in the characteristics, thedescription of the configurations and the effects for each FIG. 14 willbe made. For this reason, the description of each FIG. 14 is replacedwith the description of each FIG. 13, and thus, the redundantdescription is omitted.

A plurality of the examples that are the examples of the shape of thedifferent characteristic region W of the second embodiment and modifiedexamples thereof have been described with reference to the divisionalconfiguration example of the transmission/reflection region of thedichroic mirror illustrated in each FIG. 14 as described above. Inaddition, the modified examples thereof can also be applied to the casewhere the optical axis 1 of the light source 21 is offset with respectto the optical axis 3 having a mirror relationship with the optical axis2 of the condenser lens 25 as illustrated in FIG. 10 of the fourthembodiment.

According to the divisional configuration example of thetransmission/reflection region of the dichroic mirror of the presentembodiment described above, it is possible to achieve one of the effectsof the improvement of the B light utilization rate, the realization ofthe dimming function, the realization of the color toning function, orthe reduction of the influence of the deviation of the relative positiondue to the assembling accuracy of the optical components or combinationsthereof in response to the relationship between the shape of thedifferent characteristic region W and the irradiation regions of theplurality of light sources on the dichroic mirror.

In addition, in the description of each of FIGS. 13 and 14 of thepresent embodiment, the example in which the irradiation region E21-1and the irradiation region E21-2 do not overlap with each other has beendescribed. However, the irradiation region E21-1 and the irradiationregion E21-2 may partially overlap with each other, and even this caseis a mode of a modified example of the present embodiment. At this time,if the ratio between the wide-area characteristic region M and thedifferent characteristic region W in each irradiation region satisfiesthe above description, it is possible to achieve the same effects asthose described above.

Sixth Embodiment

In the fifth embodiment, the two lasers are used as the light source ofthe projector, and in contrast, in the present embodiment, a case wherethree lasers are used as the light source of the projector will bedescribed.

FIG. 15 is a schematic configuration diagram of a light source portionof the light source apparatus according to the present embodiment. InFIG. 15, in the configuration of the light source apparatus illustratedin FIG. 2A, FIG. 5, FIG. 7 or FIG. 10, three light sources 21-1, 21-2,and 21-3 are used, the respective light sources are driven by a powersupply 1 (20-1), a power supply 2 (20-2) and a power supply 3 (20-3),and a controller 11 for controlling the respective power supplies 1, 2and 3 is provided.

FIG. 16 is a diagram illustrating a divisional configuration of thetransmission/reflection region of the dichroic mirror corresponding tothe first embodiment (the configuration of FIG. 2A) and a modificationthereof. FIG. 16(a) is a configuration corresponding to the firstembodiment. In FIG. 16(a), an irradiation region E21-1 irradiated withthe B light from the light source 21-1 is provided in the left-side Btransmitting/Y reflecting region (wide-area characteristic region M), anirradiation region E21-2 irradiated with the B light from the lightsource 21-2 is provided in the region that extends over the left-side Btransmitting/Y reflecting region (wide-area characteristic region M),the totally reflecting region (different characteristic region W), andthe right-side B transmitting/Y reflecting region (wide-areacharacteristic region M, and an irradiation region E21-3 irradiated withthe B light from the light source 21-3 is provided in the right-side Btransmitting/Y reflecting region (wide-area characteristic region M).Since the ratio between the wide-area characteristic region M and thedifferent characteristic region W in the irradiation region E21-2 andthe ratios between the wide-area characteristic region M and thedifferent characteristic region W in the irradiation region E21-1 andthe irradiation region E21-3 (in the drawing, 0% for the differentcharacteristic region W) are different, the ratio of the B light to theY light output from the light source apparatus 2 is changed by changingthe intensities of the lasers of the light sources 21-1, 21-2, and 21-3,so that it is possible to realize the color toning function and thedimming function.

FIG. 16(b) is a modified example of the region division of FIG. 16(a),and unlike FIG. 16(a), the totally reflecting region which is adifferent characteristic region W is wide in the width direction of thepaper and corresponds to the region (corresponding to the region I inFIG. 3(c)) in which the irradiation region E21-1 irradiated with the Blight from the light source 21-1, the irradiation region E21-2irradiated with the B light from the light source 21-2, and theirradiation region E21-3 irradiated with the B light from the lightsource 21-3 are combined. With this configuration, similarly to thedescription of FIG. 13(b), it is possible to set β=1 in the B light useefficiency. Accordingly, it is possible to increase the B light useefficiency.

In addition, in the configuration of FIG. 16(a), when the power supply20-2 fails, only the light that has passed through the wide-areacharacteristic region M in the light incident on the dichroic mirrorfrom the light source is used, and thus, only the Y light is output fromthe light source apparatus 2, so that it is impossible to reproducewhite light. In contrast, in the configuration of FIG. 16(b), thetotally reflecting region which is a different characteristic region Wcovers all of the irradiation region E21-1, the irradiation regionE21-2, and the irradiation region E21-3.

Accordingly, in the configuration of FIG. 16(b), even in a case whereone of the plurality of power supplies for controlling the laser lightsource fails, it is possible to avoid the phenomenon where the lightoutput from the light source apparatus 2 becomes one of the B light andthe Y light.

In addition, FIG. 16(c) is a modified example of the region division. InFIG. 13(c), the number of irradiation regions of the plurality of laserlight sources is two, and in contrast, in the configuration of FIG.16(c), the number of irradiation regions E21-1, E21-2, and E21-3 isincreased to three. In addition, all the ratios between the wide-areacharacteristic region M and the different characteristic region W in thethree irradiation regions are changed.

Then, by variably controlling the light intensity of the light source21-1, the light intensity of the light source 21-2, and the lightintensity of the light source 21-3, it is possible to control both thecolor and the intensity of the light output from the light sourceapparatus 2, and since the number of divided regions is larger than thatof FIG. 13(c), it is possible to improve the resolution of the controlof the color and intensity.

In addition, FIG. 16(d) is a modified example of the region division. Inthe example of FIG. 16(d), similarly to the example of FIG. 16(c), theratio between the wide-area characteristic region M and the differentcharacteristic region W in the irradiation region E21-1 the ratiobetween the wide-area characteristic region M and the differentcharacteristic region W in the irradiation region E21-2, and the ratiobetween the wide-area characteristic region M and the differentcharacteristic region W is different from the ratio between thewide-area characteristic region M and the different characteristicregion W in the irradiation region E21-3 are allowed to be differentfrom each other. Therefore, similarly to the example of FIG. 16(c), itis possible to control both the color and the light intensity of thelight output from the light source apparatus 2 by variably controllingthe light intensity of the light source 21-1, the light intensity of thelight source 21-2, and the light intensity of the light source 21-3, andsince both the color and the intensity can be controlled, and the numberof divided regions is larger than that in FIG. 13(d), it is possible toimprove the resolution of the control of the color and the intensity.

In addition, in the example of FIG. 16(d), the different characteristicregions W (totally reflecting regions) have independent shapes for therespective irradiation regions from the three light sources. Inaddition, the different characteristic regions W are provided atpositions apart from the boundary of each irradiation region.Accordingly, it is possible to provide a configuration in which, due tothe assembling accuracy of the optical components, even if the relativepositions of the different characteristic region W of the dichroicmirror to the position of the irradiation region E21-1, the position ofthe irradiation region E21-2, and the position of the irradiation regionE21-3 are deviated in the horizontal direction or deviated in thevertical direction, the ratio between the wide-area characteristicregion M and the different characteristic region W in the irradiationregion E21-1, the ratio between the wide-area characteristic region Mand the different characteristic region W in the irradiation regionE21-2, and the ratio between the ratio between the wide-areacharacteristic region M and the different characteristic region W in theirradiation region E21-3 are hard to change.

That is, the example of FIG. 16(d) is a preferable mode because it ispossible to achieve both the realization of the color toning functionand the dimming function of the light output from the light sourceapparatus 2 and the reduction of the influence of the deviation betweenthe position of the irradiation region E21-1, the position of theirradiation region E21-2, and the position of the irradiation regionE21-3 and the relative position of the different characteristic region Wof the dichroic mirror due to the assembly accuracy of the opticalcomponents, and the like.

In addition, in the example of FIG. 16(d), since the differentcharacteristic region W is included in the region (region I) in whichthe irradiation region E21-1 and the irradiation region E21-2 and theirradiation region E21-3 are combined, there is also an advantage inthat the B light utilization rate is high.

As described above, a plurality of the examples that are the examples ofthe shape of the different characteristic region W of the firstembodiment (the configuration of FIG. 2A) and the modified examplesthereof have been described with reference to FIG. 16. In addition, themodified examples thereof can also be applied to the case where theoptical axis 1 of the light source 21 is offset with respect to theoptical axis 3 having a mirror relationship with the optical axis 2 ofthe condenser lens 25 as illustrated in FIG. 7 of the third embodiment.

In addition, FIG. 17 is a diagram illustrating a divisionalconfiguration of the transmission/reflection region of a dichroic mirrorcorresponding to the second embodiment and modified examples thereof.FIG. 17(a) is a configuration corresponding to the second embodiment.FIG. 17(a) illustrates the example of a case where the configurationillustrated in FIG. 15 is employed as the light source 21 in theconfiguration illustrated in FIG. 5 according to the second embodiment,and FIGS. 17(b), 17(c), and 17(d) are the modified examples thereof.

Herein, the examples of the divisional configuration of thetransmission/reflection region of the dichroic mirror illustrated inFIGS. 17(a), 17(b), 17(c), and 17(d) are obtained from the examples ofthe divisional configuration of the transmission/reflection region ofthe dichroic mirror illustrated in FIGS. 16(a), 16(b), 16(c), and FIG.16(d) by replacing the characteristics of the wide-area characteristicregion M with B reflecting/Y transmitting and replacing thecharacteristics of the different characteristic region W with totallytransmitting so as to correspond to the second embodiment. If thedescription of FIG. 16 is replaced in response to the change in thecharacteristics, the description of the configurations and the effectsfor each FIG. 17 will be made. For this reason, the description of eachFIG. 17 is replaced with the description of each FIG. 16, and thus, theredundant description is omitted.

A plurality of the examples that are the examples of the shape of thedifferent characteristic region W of the second embodiment and themodified examples thereof have been described with reference to thedivisional configuration example of the transmission/reflection regionof the dichroic mirror illustrated in each FIG. 17 as described above.In addition, the modified examples thereof can also be applied to thecase where the optical axis 1 of the light source 21 is offset withrespect to the optical axis 3 having a mirror relationship with theoptical axis 2 of the condenser lens 25 as illustrated in FIG. 10 of thefourth embodiment.

According to the divisional configuration example of thetransmission/reflection region of the dichroic mirror of the presentembodiment described above, it is possible to achieve one of the effectsof the improvement of the B light utilization rate, the realization ofthe dimming function, the realization of the color toning function, orthe reduction of the influence of the deviation of the relative positiondue to the assembling accuracy of the optical components or combinationsthereof in response to the relationship between the shape of thedifferent characteristic region W and the irradiation regions of theplurality of light sources on the dichroic mirror.

In addition, in the dimming function and the color toning function, theresolution can be further improved.

In addition, in the description of FIGS. 16 and 17 of the presentembodiment, the example in which the irradiation region E21-1, theirradiation region E21-2, and the region E21-3 do not overlap with eachother has been described. However, the irradiation region E21-1, theirradiation region E21-2, and the region E21-3 may partially overlapwith each other, and even this case is a mode of a modified example ofthe present embodiment. At this time, if the ratio between the wide-areacharacteristic region M and the different characteristic region W ineach irradiation region satisfies the above description, it is possibleto achieve the same effects as those described above.

Seventh Embodiment

In the present embodiment, an embodiment in which a more suitableprojector can be realized by using an alumina ceramic plate as adiffusion plate will be described.

FIG. 18 is a schematic diagram illustrating a cross-sectional view of analumina ceramic plate as the diffusion plate 26 in the presentembodiment. As illustrated in FIG. 18, the alumina ceramic plate is anaggregate of alumina particles having a random shape, and has a propertythat allows incoming light to pass through and reflect at random withoutirregularity processing on the reflecting surface. For this reason, forexample, as illustrated in the figure, even the outgoing lights Ao andBo emitted at the same angle include not only the light passing throughthe same path but also the light Ai and Bi passing through differentpaths. That is, since even the light emitted at the same angle includeslight having different optical path lengths, this is effective inreducing speckle noise.

Herein, the mechanism of the diffusion plate will be described. FIG. 19is a diagram for explaining the light focusing angle θi of the incominglight and the diffusion angle θo of the outgoing light with respect tothe diffusion plate in the present embodiment. As illustrated in FIG.19(a), light incident on the diffusion plate 26 is focused by thecondenser lens 25 and is incident on the diffusion plate 26 at the lightfocusing angle θi. In addition, as illustrated in FIG. 19(b), theoutgoing light from the diffusion plate 26 is emitted at a diffusionangle θo. Herein, since light generally diffuses, the definition of thediffusion angle θo in the present embodiment will be described withreference to FIG. 20. FIG. 20 illustrates the intensity distribution ofthe light emitted from the diffusion plate 26, the vertical axisrepresents the intensity, and the horizontal axis represents the angleof the diffusion light with respect to the normal line to the diffusionplate. As illustrated in FIG. 20, the intensity decreases as theposition deviates from the center position, when the peak intensity ofthe outgoing light is set to 100%, the angle at which the intensity ofthe outgoing light becomes 50% is defined as the diffusion angle θo ofthe outgoing light of the diffusion plate in the present embodiment.

Next, the relationship of the use efficiency of the B light between thelight focusing angle θi of the incoming light, the diffusion angle θo ofthe outgoing light, illustrated in FIG. 19 is calculated. Herein, inorder to simplify the calculation, FIG. 21 illustrates an explanatorydiagram of a case where the region I, the region O, the region WI, andthe region WO of the dichroic mirror 24 illustrated in FIG. 3C areconverted into a model of a circular region. FIG. 21 illustrates a modelof a case where the area SWI=the area SWO (β=1) where the use efficiencyof the B light is the highest, as described above. In addition, as theshapes of the different characteristic regions W, any of the shapesillustrated in FIGS. 13B, 13C, and 13D, FIGS. 14B, 14C, and 14D, FIGS.16B, 16C, and 16D, and FIGS. 17B, 17C, and 17D can be converted into thecircular model in FIG. 21.

FIG. 22 illustrates an optical path near the diffusion plate in thepresent embodiment. In FIG. 22, Xi denotes the diameter of the circularregion of the incoming light, and Xo denotes the diameter of thecircular region of the outgoing light. In addition, L is a focal length.

Herein, as described in the first embodiment, the B light utilizationrate E2 in the configuration of FIG. 3B is R2×T2=R2×(1−(R2×β/α), and theB light utilization rate E1 in the configuration illustrated in FIG. 3Athat does not employ the region division of the transmission/reflectioncharacteristics and the diffusion plate is (R1×T1)=R1×(1−R1). Inaddition, the condition for E2>E1 can be converted into(SO−SWO)/SO>(SI−SWI)/SI as described above in the first embodiment. Thisequation can be further converted into 1−SWO/SO>1−SWI/SI, and bysubtracting 1 from both sides and tidying up the inequality signs, theequation can be converted into SWO/SO<SWI/SI and can be converted intoSO/SWO>SI/SWI. Furthermore, when SWO/SWI is multiplied on both sides,this can be converted into SO/SWI>(SI/SWI)×(SWO/SWI).

Herein, SO/SWI denotes the ratio of the area SO (that is, thecross-sectional area of the B light beam returning from the condenserlens 25) of the region O of the B diffusion light returning to thedichroic mirror to the area (that is, the cross-sectional area of the Blight beam toward the condenser lens 25) of SWI, which is the size ofthe different characteristic region WI in the incident region I of the Blight in the dichroic mirror and represents the effect of increasing thecross-sectional area of the B light beam by the function of thecondenser lens 25 and the diffusion plate 26. Furthermore, SI/SWI is areciprocal of the real reflectance R2 in the configuration of FIG. 3B.In addition, SWO/SWI is β described above. Therefore,SO/SWI>(SI/SWI)×(SWO/SWI) can be converted into SO/SWI>β/R2.

Herein, in FIG. 3A without employing the region division of thetransmission/reflection characteristic and the diffusion plate describedabove, the suitable B light reflectance is R1=0.2, and as illustrated inFIG. 21, in a case where the different characteristic region WI isincluded in the incident region I, since β=1, SO/SWI>1/0.2, that is,SO/SWI>5. That is, in order to exceed the B light utilization rate inthe type of the related art, by the function of the diffusion plate 26,the area ratio of SO/SWI needs to exceed 5 times.

Since SO is the area of the incident region O of the diffusion light andSWI is the area of the totally reflecting region WI which is a differentcharacteristic region in the incident region I of the B incoming light,SO=π (Xo/2)² and SWI=π(Xi/2)² in FIG. 22. Therefore, the condition thatthe area ratio of SO/SWI exceeds 5 times is π (Xo/2)²>5×π (Xi/2)². Thatis, Xo>√5×Xi.

At this time, in FIG. 22, when the light focusing angle θi isrepresented by Xi and the focal length of the condenser lens 25 isrepresented by L, the light focusing angle θi=2×arcsine((Xi/2)/L). Inaddition, when the diffusion angle θo is represented by Xo and the focallength of the condenser lens 25 is represented by L, the diffusion angleθo=2×arcsine((Xo/2)/L). In consideration of these equations, thecondition of the diffusion angle satisfying Xo>√5×Xi, which is thecondition that the area ratio of SO/SWI exceeds 5 times, isθo>2×arcsine((√5×Xi/2)/L).

Herein, as a whole scale of the optical system of the =light sourceapparatus 2, in principle, various optical path lengths and light beamapertures at which the efficiency becomes suitable are determined on thebasis of the aperture size of the panel used for the image displayelements 6R, 6G, and 6B, and thus, some allowable width exists dependingon the design of each optical element. As a specific example, in a casewhere the aperture size of the panel used for the image display elements6R, 6G, and 6B is about 0.6 inches, for example, the focal length L inFIG. 22 is preferably about 15 mm, and the area SWI in FIG. 21 ispreferably about 35 square mm. In consideration of the possibility ofusing a panel having a size of, for example, about 0.3 inches to 1.0inch depending on the model of the projector as the aperture size of thepanel used for the image display elements 6R, 6G, and 6B, and further inconsideration that there is a width in the design of each opticalelement of the optical system, the allowable range of the focal length Lin FIG. 22 is about 12 mm to 30 mm, and the allowable range of the areaSWI in FIG. 21 is about 25 square mm to 42 square mm. In addition, ifthe allowable range of the area SWI of about 25 square mm to 42 squaremm is converted into the range of Xi, the allowable range of Xi is 5.64mm to 7.31 mm.

Since the characteristics of the diffusion angle of the diffusion plate26 cannot be easily adjusted by the model of the projector as theaperture size of the panel used for the image display elements 6R, 6G,and 6B and the design parameters of each optical element of the opticalsystem of the light source apparatus 2, in order to reduce the cost ofthe diffusion plate 26, it is preferable to use a common type ofdiffusion plate for a plurality of projector models having differentaperture sizes of panels. Then, the allowable range of the focal lengthL in FIG. 22 is about 12 mm to 30 mm, and the allowable range of thearea SWI in FIG. 21 is about 25 square mm to 42 square mm (5.64 mm to7.31 mm in the allowable range of Xi), and in the entire range of boththe allowable ranges, it is necessary to obtain the condition of thediffusion angle where the area ratio of SO/SWI exceeds 5 times.

That is, in the entire ranges of the allowable range of the focal lengthL of about 12 mm to 30 mm and the allowable range of Xi of 5.64 mm to7.31 mm, diffusion angle θo satisfying the above-described conditionalexpression of θo>2×arcsine((√5×Xi/2))/L) may be obtained. In theabove-described conditional expression, the diffusion angle θo increasesas L decreases, and the diffusion angle θo increases as Xi increases.Then, in the above-described allowable ranges of L and Xi, the requiredvalue of the diffusion angle θo becomes the largest value in a casewhere L is 12 mm which is the minimum value of the allowable range andXi is 7.31 mm which is the maximum value of the allowable range (thearea SWI is 25 square mm, which is the minimum value of the allowablerange). Therefore, when L=12 mm and Xi=7.31 mm are substituted for theconditional expression θo>2×arcsine((√5×Xi/2)/L),θo>2×arcsine((√5×7.31/2)/12). When this is calculated, θo>86°.

That is, the diffusion plate used in the projector according to thepresent embodiment is a diffusion plate capable of exceeding the B lightutilization rate in the type of the related art, and as the condition ofthe lower-cost diffusion plate, the diffusion plate of the typesatisfying the diffusion angle θo>86° may be used.

Next, FIG. 23 is a type comparison table comparing the case of using analumina ceramic plate and the case of other types as examples of thediffusion plate used in the projector according to the presentembodiment. In FIG. 23, as the types of the diffusion plate, four typesare compared. The type A is a type in which the above-described aluminaceramic plate is used as a reflection-type diffusion plate. The type Bis a type in which a frost glass in which both surfaces of the glassroughened by sandblasting or etching and a mirror is added to the backsurface thereof is used as a reflection-type diffusion plate. The type Cis a type in which a metal subjected to surface irregularity processingis used as a reflection-type diffusion plate. Furthermore, the type D isa type in which a frost glass in which one surface of the glass isroughened by sandblasting or etching and a mirror is added to the backsurface thereof is used as a reflection-type diffusion plate.Furthermore, the type D is a type in which a frost glass in which oneside of the glass roughened by sandblasting or etching and a mirroradded to the back surface thereof is used as a reflection-type diffusionplate (in contrast to the type B, this type may be referred to as a typein which, in the frost glass of this type, only one surface of the glassis changed).

Herein, FIG. 23 illustrates the results of comparison of the substratematerial, the processing contents, the diffusion angle θo of theoutgoing light, the amount of noise such as speckle, and the cost foreach type. First, with respect to the substrate material, in the type A,only the alumina ceramic plate is used, and in the type C, only themetal is used. The type B and the type D require a transparent glass anda mirror. Therefore, in consideration of the cost of the substratematerial portion, the type B and the type D which require a plurality ofsubstrate materials are relatively disadvantageous.

In addition, with respect to the processing contents, the type A can bemanufactured only by pressing alumina ceramic, and does not requireirregularity processing. This is advantageous in terms of processingcost. In addition, the other types B, C, and D require irregularityprocessing on the reflecting surface, which is disadvantageous in termsof the processing cost.

In addition, with respect to the diffusion angle θo of the outgoinglight in the alumina ceramic type of the type A, the outgoing light thatis diffused at random is generated without depending on the lightfocusing angle of the incoming light, and the diffusion angle θo of theoutgoing light is as large as about 120°.

Next, in the type B, the diffusion angle of the outgoing light dependson the light focusing angle of the incoming light, and the diffusionangle of the outgoing light is obtained by adding the effect of theincrease of the diffusion angle of the diffusion plate to the lightfocusing angle of the incoming light. For example, if the light focusingangle of the incoming light is about 14°, the effect of the increase ofthe diffusion angle of the type B is about 30°, so that the finaldiffusion angle θo of the outgoing light is about 14°+about 30°=about44°.

In addition, in the type C, random diffused outgoing light is generatedwithout depending on the light focusing angle of the incoming light, andthe diffusion angle θo of the outgoing light is about 40°.

Finally, in the type D, the diffusion angle of the outgoing lightdepends on the light focusing angle of the incoming light, and thediffusion angle of the outgoing light is obtained by adding the effectof the increase of the diffusion angle of the diffusion plate to thelight focusing angle of the incoming light. For example, if the lightfocusing angle of the incoming light is about 14°, the effect of theincrease of the diffusion angle of the type D is about 6°, so that thefinal diffusion angle θo of the outgoing light is about 14°+about6°=about 20°.

Herein, when comparing the diffusion angles of the outgoing light in thetypes A, B, C, and D with the above-described conditional expressionθo>86° of the diffusion angle of the low-cost diffusion plate in whichthe B light utilization rate exceeds that in the type of the relatedart, it can be said that only the alumina ceramic type of the type Aexceeds the condition, and this type is more suitable as the diffusionplate used in the projector according to the present embodiment. In theother three types, this condition is not satisfied.

Next, with respect to the noise such as speckles, the type A and thetype B are small, while the type C and the type D are medium or large.In terms of this point, the alumina ceramic type of the type A isrelatively good

Finally, with respect to the overall cost in consideration of thesubstrate material and the processing contents, the type B and the typeD, which require a plurality of substrate materials, need to beexpensive, but the type A and the type C are relatively inexpensive. Interms of overall cost, the alumina ceramic type of the type A isrelatively good.

As described above, the diffusion plate used in the projector accordingto the present embodiment is advantageous in terms of any of thecomparison items, and in particular, the diffusion angle θo of theoutgoing light sufficiently satisfies the above-described conditionalexpression of the diffusion angle, and noise such as speckle is alsoreduced, and thus, it can be understood that it is advantageous toemploy a relatively inexpensive alumina ceramic type diffusion plate.

According to the projector according to the present embodiment describedabove, it is possible to provide an inexpensive projector having ahigher B light utilization rate by using a diffusion plate having adiffusion angle of the outgoing light satisfying θo>86°. In particular,by employing a diffusion plate using alumina ceramic, it is possible torealize a more suitable projector.

Although the embodiments have been described above, the presentinvention is not limited to the above-described embodiments, and variousmodified examples are included. In addition, the above-describedembodiments have been described in detail for easy understanding of thepresent invention, and thus, the embodiments are not necessarily limitedto those having all the configurations described above. In addition, aportion of the configurations of the embodiments can be replaced withother configurations.

REFERENCE SIGNS LIST

-   1 Optical system-   2 Light source apparatus-   3 Illumination optical system-   4 Color separating optical system-   6R, 6G, 6B Image display element-   7 Light combining optical system-   8 Projection lens-   21, 21-1, 21-2, 21-3 Light source-   22, 23 Lens-   24, 91, 92, 93 Dichroic mirror-   25, 27 Condenser lens-   26 Diffusion plate-   28 Phosphor wheel-   29 Motor

The invention claimed is:
 1. A projector comprising: a white lightgenerator that uses a blue laser as a light source to generate bluelight and yellow light based on the blue laser and generates white lightincluding the generated blue light and yellow light; and an opticalsystem that modulates light based on the white light generated by thewhite light generator with an image display element and projects themodulated light, wherein the white light generator is configured toinclude: a dichroic mirror that is irradiated with the blue light fromthe blue laser as the light source; a first condenser lens that focusesblue light being reflected by or passing through the dichroic mirror; adiffusion plate that diffuses the blue light focused by the firstcondenser lens; a second condenser lens that focuses the blue lightpassing through or being reflected by the dichroic mirror; a phosphorthat is irradiated with the blue light focused by the second condenserlens to emit yellow light, wherein the diffusion plate is an aluminaceramic plate, wherein the dichroic mirror has a first region having acharacteristic of transmitting one of the blue light and the yellowlight and reflecting the other and a second region having acharacteristic of reflecting or transmitting both the blue light and theyellow light, wherein the blue light included in the white light outputby the white light generator is obtained by allowing the blue lightdiffused by the diffusion plate to pass through the first condenser lensand performing reflection or transmission of the dichroic mirror, andwherein the yellow light included in the white light output by the whitelight generator is obtained by allowing the yellow light emitted fromthe phosphor to pass through the second condenser lens and performingreflection or transmission of the dichroic mirror.
 2. A projectorcomprising: a white light generator that uses a blue laser as a lightsource to generate blue light and yellow light based on the blue laserand generates white light including the generated blue light and yellowlight; and an optical system that modulates light based on the whitelight generated by the white light generator with an image displayelement and projects the modulated light, wherein the white lightgenerator is configured to include: a dichroic mirror that is irradiatedwith the blue light from the blue laser as the light source; a firstcondenser lens that focuses blue light being reflected by or passingthrough the dichroic mirror; a diffusion plate that diffuses the bluelight focused by the first condenser lens; a second condenser lens thatfocuses the blue light passing through or being reflected by thedichroic mirror; a phosphor that is irradiated with the blue lightfocused by the second condenser lens to emit yellow light, wherein thediffusion angle θo of the outgoing light of the diffusion plate exceeds86°, wherein the dichroic mirror has a first region having acharacteristic of transmitting one of the blue light and the yellowlight and reflecting the other and a second region having acharacteristic of reflecting or transmitting both the blue light and theyellow light, wherein the blue light included in the white light outputby the white light generator is obtained by allowing the blue lightdiffused by the diffusion plate to pass through the first condenser lensand performing reflection or transmission of the dichroic mirror, andwherein the yellow light included in the white light output by the whitelight generator is obtained by allowing the yellow light emitted fromthe phosphor to pass through the second condenser lens and performingreflection or transmission of the dichroic mirror.
 3. The projectoraccording to claim 2, wherein the diffusion plate is an alumina ceramicplate.
 4. The projector according to claim 1, wherein the dichroicmirror has a region having blue light transmission/yellow lightreflection characteristics as the first region and has a region oftotally reflecting characteristic as the second region, wherein the bluelight included in the white light output from the white light generatoris light obtained by allowing the blue light diffused by the diffusionplate to pass through the first condenser lens, to be irradiated to thedichroic mirror, and to pass through the first region, and wherein theyellow light included in the white light output from the white lightgenerator is light obtained by allowing the yellow light emitted fromthe phosphor to pass through the second condenser lens, to be irradiatedto the dichroic mirror, and to be reflected by the first region.
 5. Theprojector according to claim 1, wherein the dichroic mirror has a regionhaving blue light reflection/yellow light transmission characteristicsas the first region and has a region of totally transmittingcharacteristic as the second region, wherein the blue light included inthe white light output from the white light generator is light obtainedby allowing the blue light diffused by the diffusion plate to passthrough the first condenser lens, to be irradiated to the dichroicmirror, and to be reflected by the first region, and wherein the yellowlight included in the white light output from the white light generatoris light obtained by allowing the yellow light emitted from the phosphorto pass through the second condenser lens, to be irradiated to thedichroic mirror, and to pass through the first region.
 6. The projectoraccording to claim 2, wherein the dichroic mirror has a region havingblue light transmission/yellow light reflection characteristics as thefirst region and has a region of totally reflecting characteristic asthe second region, wherein the blue light included in the white lightoutput from the white light generator is light obtained by allowing theblue light diffused by the diffusion plate to pass through the firstcondenser lens, to be irradiated to the dichroic mirror, and to passthrough the first region, and wherein the yellow light included in thewhite light output from the white light generator is light obtained byallowing the yellow light emitted from the phosphor to pass through thesecond condenser lens, to be irradiated to the dichroic mirror, and tobe reflected by the first region.
 7. The projector according to claim 2,wherein the dichroic mirror has a region having blue lightreflection/yellow light transmission characteristics as the first regionand has a region of totally transmitting characteristic as the secondregion, wherein the blue light included in the white light output fromthe white light generator is light obtained by allowing the blue lightdiffused by the diffusion plate to pass through the first condenserlens, to be irradiated to the dichroic mirror, and to be reflected bythe first region, and wherein the yellow light included in the whitelight output from the white light generator is light obtained byallowing the yellow light emitted from the phosphor to pass through thesecond condenser lens, to be irradiated to the dichroic mirror, and topass through the first region.
 8. The projector according to claim 3,wherein the dichroic mirror has a region having blue lighttransmission/yellow light reflection characteristics as the first regionand has a region of totally reflecting characteristic as the secondregion, wherein the blue light included in the white light output fromthe white light generator is light obtained by allowing the blue lightdiffused by the diffusion plate to pass through the first condenserlens, to be irradiated to the dichroic mirror, and to pass through thefirst region, and wherein the yellow light included in the white lightoutput from the white light generator is light obtained by allowing theyellow light emitted from the phosphor to pass through the secondcondenser lens, to be irradiated to the dichroic mirror, and to bereflected by the first region.
 9. The projector according to claim 3,wherein the dichroic mirror has a region having blue lightreflection/yellow light transmission characteristics as the first regionand has a region of totally transmitting characteristic as the secondregion, wherein the blue light included in the white light output fromthe white light generator is light obtained by allowing the blue lightdiffused by the diffusion plate to pass through the first condenserlens, to be irradiated to the dichroic mirror, and to be reflected bythe first region, and wherein the yellow light included in the whitelight output from the white light generator is light obtained byallowing the yellow light emitted from the phosphor to pass through thesecond condenser lens, to be irradiated to the dichroic mirror, and topass through the first region.